The court ruling in NL (which lead to a (temporary) forced block from ISP's of the website) was that despite them technically not hosting anything illegal, they are definitely an, let's call it, "accessory to piracy", a middle man so to speak. You know, like how Silk Road was just a middle man for drug deals - the website itself didn't host any drugs. Not that that's technically possible (yet), but you get the idea.